Attenuator



April 10, 1951 A. J. HYATT 2,548,024

ATTENUATOR Filed Dec. 2, 1949 2 Sheets-Sheet 1 INVENTOR ATTORNEY April10, 1951 A. J. HYATT 2,548,024

ATTENUATOR Filed Dec. 2, 1949 2 Sheets-Sheet 2 z/ If Z7 3 .7/

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1a 17 H W 11 Z W y? Kl Ill I I I D l J6 INVENTOR W Mil A INA l [I W W a2ATTORNEY Patented Apr. 10, 1951 ATTENUATOR Arnold J. Hyatt, RichmondHill, N. Y., assignor to A. F. Smuckler & 00., Inc., Brooklyn, N. Y., acorporation of New York Application December 2, 1949, Serial No. 180,791

1 Claim. 1

The present invention relates generally to a radio frequency stepattenuator and is more particularly directed to an apparatus of thistype which may be employed for ultra high frequency waves or microwaves.In order that the attenuator may be useful in these ranges theconductors or resistances employed are of the coaxial type. It is one ofthe objects of the present invention, therefore, to provide anattenuator of simple and rugged construction and which eniploys theaxial type of resistors.

Another object of the invention is to provide a completely shieldedattenuator of the type described.

A still further object of the invention is to provide a variableattenuator having a range of 8 decibels operable in four equal steps.

Another object of the invention is to provide an attenuator cf the typedescribed in which the error of deviation to frequency characteristicsshall be less than 10% throughout the frequency range of 70 kilocyclesto 609 megacycles.

Another still further object is to provide an attenuator which may carrya load or receive an input consisting of 100 volt pulses with a 0.125%duty cycle.

A still further object of the present invention is to provide anattenuator of the class described in which the effects of temperature,humidity, and voltage on its accuracy is minimized.

For the purpose of a fuller and more detailed description of the presentinvention and of its many objects and inventions, reference is had tothe accompanying drawings and the following specification whichillustrate one specific embodiment of the present invention; it beingunderstood that variations thereof falling within the scope of theappended claim will be apparent to persons skilled in the art.

In the drawings:

Fig. 1 is a front end View of the attenuator.

Fig. 2 is a longitudinal sectional view on line 2-2 of Fig. 1.

Fig. 3 is a transverse sectional view on line 3-3 of Fig. 2.

Figs. 4, 5, 6, 7, and 8 are partial longitudinal views on each of theresistor circuits respectively.

Fig. 9 is a detail sectional view.

In its broad outlines the present attenuator consists essentially of ametal housing and a turret disposed within the housing. The turret,preferably a solid cylindrical metal body, is pro vided with an outerand an inner series of circularly disposed passages or barrels extendingfrom end to end. Each pair of passages or barrels,

one from the outer and one from the inner series, disposed radially withreference to each other, are connected to each other by a recess in oneend of the turret. Thus the pair of barrels with the recess form aU-shaped conduit for the reception of conductor-resistors of the coaxialtype. The free ends of the barrels carry connectors of the coaxial typefor separably connecting with a cooperating pair of fixed connectorscarried by an end plate of the housing or casing. In its normal positionthe turret is maintained against accidental rotation and a selected pairof coaxial conductor-resistors are in engagement with the fixedconnectors on the casing and the cables attached thereto may, therefore,receive the load or input and pass the same through the desired orconnected pair of attenuating conductors or resistors. When it isdesired to change the attenuation, the turret is first moved axially todisengage the turret from the fixed connectors on the end plate of thecasing and the turret is then rotated into the desired position for theengagement of another pair of attenuating resistances with the fixedconnectors on the end plate of the casing or housing.

With the above outline of the broad aspects of the construction of thepresent attenuator, a more detailed description of the several elementswill now give a full understanding of the invention.

The metal housing or casing comprises a tube or cylinder ID, a front endplate l I, and a rear end plate Ill. The end plates have lower straightedges and are otherwise shaped as shown in Figs. 1 and 3, and haveattached thereto feet or brackets 3. The inner faces of the front andrear plates are each provided with an annular shoulder 14 to receive thetube l0. Tie rods [5 connect the marginal portions of the end plates l land I2 and the assembly is held firmlysecured by the cap nuts I 6. Thedetent H is mounted on the outer face of the tube or cylinder l0 and itsdetent lug l8 and extends interiorly of the tube for engagement with oneof the grooves IS in the turret 20 to prevent its accidental rotation asshown in Figs. 2 and 3.

The turret 20 is a cylindrical body of metal, such as brass or the like,which may be provided with the circular series of passages 2| to reduceits weight. One end of the shaft 22 is lodged in the bearing 23 carriedby the rear plate l2 and the other end of the shaft 22 passes through acorresponding opening in the end plate H and carries the handle 24 whichis provided with a pointer 25. The exposed face of the end plate 55 isprovided with several indicia as shown in Fig. 1 to indicate the steppositions of the shaft and also to indicate the degree of attenuation ineach of these positions. The turret is held firmly secured to the shaft22 by the set screw 26. The forward end of the turret is provided with arecess 2? which receives the helical spring 28 interposed between thebottom of the recess and the inner face of the end plate ii, therebyholding the turret and its shaft in the normal or engaged position shownin Fig. 2. tainers 29 are disposed at the ends of the spring 28.

The outer cylindrical face of the turret 20 is provided with a circularchannel 39 designed to receive the upper end of the detent 88 to permitrotation of the turret 2t. Relatively short longitudinal grooves l9branch out from channel 39 and serve to receive the detent I8 when theturrot is in an engaged position. When it is desired to switch or changethe position of the turret, it is moved axially against the spring 28until,

the detent it? enters, the channelor passage 30..

The turret may then be rotated to desired position.

tion 33 at its rear end which receives the coaxial type of separableconnector 3 5. The shoulder 35,

against whichthe connector 3 5 abuts, preferably extends somewhat intothe passage or bore 32.

The bores or barrels 32 receive coaxial conductors or coaxial typeattenuating resistors and.

the recess 3! receives the coaxial jumpe conductor 36 for connecting thetwo longitudinal coaxial conductorsor resistors. Thus each pair ofparallel and radially spaced longitudinal barrels, together with itsassociated recess 3i, form a U-shaped passage or conduit for housingcoaxial attenuator conductor-resistors.

All of the jumper conductors Siiare of the same construction. They eachcomprise a short length of insulation filled coaxial cable 37 which joina pair of short metal cylinders 38 disposed in the forward end ofeachbarrel or bore 32-. The central conductor 39 in the jumpers extendsat each end into the cylinders 38 and the ends are bent downwardly asshown in dotted lines in Fig. 4 and enter suitable recesses in the endsof the conductor-resistors disposedin the passages 32.

The conductors or the resistors disposed in the barrels 32 of the turretvary for the, purpose of varying the, degree of attenuation. Thus in onepair of barrels, which may be spoken of as the Zero pair, illustrated inFig. 4, there are no resistors and these contain thev coaxial conductorsconsisting of the coaxial conducting sleeve to and the coaxial.conductor 4|. The sleeve (it abuts the shoulder and the insulatingspacer disk 42 at the, other end. The conductor ll at one end enters arecess in the central electrode 53 of the quick detachable connector 33.t its other end the conductor M has, a reduced portion that pasIesthrough the spacer disk 42 and receives the bent end of the conductor39.

Thus in the position of zero attenuation the two barrels each carrysubstantially non-resistive coaxial cables in series with the coaxialjumper Spring re- I conductor.

a. jecting wire 61.

4 that unites the two barrels and when the turret is in this position asshown in Fig. 2, the power coming in by one of the cables 44 leaves bythe other substantially unattenuated.

The second pair of passages or barrels 32 that correspond to the 20decibel position, one carries a coaxial conductor Ml, G5, which is thesame as in the zero position. In the other passage of this pair, as willbe seen in Fig. 5, a rod and disk resistor unit is inserted in serieswith the coaxial The rod 55 is of ceramic material or other suitableinsulating material with a thin coating of resistive conducting materialand capped by conducting caps 46, each having a pro- At one end the wire47 enters a suitable recess in the end of the conductor 4|. At the otherend, the wire 41 enters the passage of the retainer lt which isinterposed between the -rod and the disk 49. The disk is made ofBakelite or any other suitable material coated with a thinreristivecoating of conductive. material. The retainer 18 has. ashoulder which abuts the dish and a reduced portion that passes. throughanopening in the diskand joins with the,

conductor 33 of the quick detachable connector.

unit. to one tenth, of its. original strength.

In. position 3 or in the. 40 decibel. position. as. shown in Fig. 6, tworod and disk units are employed in series as shown. In this the degreeof attenuation is one hundred, the signal being reduced to one hundredthits. originalstrength.

In the fourth or decibel position, as shown in Fig. 7, two rod. and diskassemblies are employed in series in oneleg of the conductor resistorand a thrd rod and disk assembly is mounted in-the other leg. Inposition 5 or in the decibel position, two such assemblies arev disposedin each leg of the resistor, as shown in Fig. 8, Inthese positions thedegree of attenuation, is 1,000 and 10,000 respectively.

The manner in which the resistor disk 49 is held in position between apair of rods 45is i1.- lustrated in Fig. 9. The retainer 28 is providedwith an axial passage receiving the wires 47 from the adjacent rods. Thereduced portion of the metallic retainer passes through the centralaper-- ture in the disk 29- and receives the metallic an nulus 5! whichbears against the other faceo the disk. Thus the disk is held betweenthe elements 48 and ti and the latter are held between the adjacent rods45. The rod resistor element 45 is a ceramic rod coated with a thinlayer of carbon originally applied in the form of a carbon paint or acarbon suspension. The shunt elements, the. apertured disks 49,, are.preferably a minimum. The rod resistors are very small in cross section,and in the present embodiment of the invention they are less than /9inch in diameter, thereby substantially eliminating the skin eirect, andthe ceramic insulating material employed is of very low power lossthereby preventing the increase of its conductance with a rise infrequency.

The rod resistor 45 employed in the present embodiment of the inventionhas a resistance of 45s ohms, and maintains an essentially resistive Inthis pofiticn the degree of attenuation is ten, the signal being reducedby. the rod and disk.

characteristic up to and including 600 megacycles and throughout therange of the attenuator. When the resistance of the rod unit isincreased, capacitance effects enter at the higher frequencies as thefrequencies approach 600 megacycles. Thus the present apparatus employsthe single rod in the 20 decibel attenuation and employs 2 or 3 or 4such rods in series in the higher attenuations. If, instead of employingseveral rod and disk units, a single rod and disk unit having a muchhigher resistance were employed, the conditions of 0 phase angle andunity power factor would not exist.

The input shunt disk elements 49 each have a resistance of 55 ohms andthe output shunt disk elements 50 each have a resistance of 50 ohms.Broadly described the present attenuation system employs a T network inwhich the resistance units in the inner conductor are each 450 ohms ofthe type described herein and the shunt units are the disks which are 55or 50 ohms as described, there being at least one such shunt diskassociated with each rod or at least one such shunt disk betweenadjacent rods.

I claim:

A shielded attenuator comprising a metal housing, a metal turretdisposed within the housing, the turret havin a series of parallelpassages, co-axial resistor conductors disposed in said passages,co-axial conductors mounted on one end of said turret and connectingadjacent resistor conductors in pairs, a connector carried by the otherend of each resistor, a pair of fixed connectors carried by the housingfor separable and selective connection with any desired pair of saidfirst mentioned connectors, and means for moving said turret intoselective engagement between said pair of fixed connectors and aselected pair of resistor connectors.

ARNOLD J. HYATT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,905,353 Potter Apr. 25, 19331,957,538 Jensen May 8, 1934 2,286,029 Van Buren June 9, 1942 2,429,401Davis Oct. 21, 1947

